This proposal addresses itself to two aspects of oral biochemistry. The first concerns the interaction between the enamel surface and the macromolecular components of saliva so as to gain fundamental insight into the formation of the organic pellicle of tooth. The second seeks to initiate an exploration of the molecular basis of bacterial adhesion to tooth surfaces. Electron spin resonance spectroscopy (ESR), having been shown to be especially appropriate to such interface studies, will be the major methodology. Its application will focus on the analysis of materials that have undergone spin-labeling procedures such as the production of free radicals by x-rays or ultraviolet radiation, the binding of transition-ion probes, and the reaction with stable nitroxide radicals.